Experimental Studies of Gas Breakdown and Electron Emission for Nanoscale Gaps at Atmospheric Pressure

Characterization of gas breakdown for microscale and smaller gaps is critical for applications requiring plasma formation (e.g. combustion and plasma medicine) and the prevention of plasma formation (e.g. microelectronics reliability). Traditionally, gas breakdown is driven by Townsend avalanche and predicted mathematically by Paschen’s law. Reducing gap distance at atmospheric pressure creates high electric fields at the cathode that strip electrons by field emission (FE) to ionize neutral gas atoms; the resulting space-charge adds to secondary electron emission 1 . A matched asymptotic analysis predicts that breakdown voltage decreases linearly with decreasing gap distance when FE drives breakdown 1 . Further reducing gap distance below a few hundred nm at atmospheric pressure leads to a third order nexus, where the solutions for FE, collisional space-charge limited current, and vacuum space-charge limited current match 2 . Thus, for smaller gaps, space-charge may impact emission prior to encountering breakdown.